1. Technical Field
This invention relates to a method and system for ascertaining the position and orientation of a camera or a display apparatus relative to a real object for use in merging a virtual data model with an image generated by the camera or display apparatus, said image comprising at least one part of the real object.
2. Background Information
Such a method and system are known in the prior art in particular in connection with so-called augmented reality systems. These permit the superimposition of computer-generated, virtual information with visual impressions of the real environment. For this purpose the visual impressions of the real world are merged with virtual information preferably by means of semitransparent data goggles worn on the head. The insertion of the virtual information or objects can be effected in contextual fashion, i.e. being adapted and derived from the real environment being viewed. The virtual information employed can basically be any type of data such as texts, images, etc. The real environment can be detected with a camera, mounted for example on the head of the user. Through the superimposition of virtual and real environments, the user has the possibility to easily carry out actual/nominal comparisons. Upon a head movement of the user of an augmented reality system, all artificial objects must be registered to the changing field of view.
During an initialization process, an object of the real environment is correlated with the camera, for example. This permits a camera image to be assigned to the real environment. The real environment can be a complex apparatus and the detected object can be a striking element of the apparatus. During a following so-called tracking process, which represents the actual working process, while for example a user of the system receives, in an employed display device, contextual information inserted at a desired position in relation to the real environment, the inserted virtual data model is registered to the movement of the user and to an associated change in his view of the real world.
Further, augmented reality technology is known from the prior art in connection with a superimposition of virtual models with reality for the purpose of checking the correctness of the models or of the reality produced according to the specification. Ranges of application are for example factory planning, e.g. as described in DE 101 28 015 A1 or DE 10 2004 046 144 A1, or automobile design, as described in DE 202 03 367 A. From the prior art devices are also known that one moves with the hand and so as to assume a viewing position into a virtual world (e.g. U.S. Pat. No. 5,436,638 A).
Such augmented reality systems or methods basically involve the recognition of the camera pose relative to reality. The camera pose is the position and orientation of the camera in space. Reality is usually present in some form as a model, for example as a 3D model which circumscribes the geometrical properties of reality or a part of reality. The 3D model can be obtained for example from a design drawing, e.g. a CAD document. The real object is usually correlated to an object coordinate system, the camera in turn to a camera coordinate system. It is generally problematic here in particular to exactly ascertain the transformation between object coordinate system and camera coordinate system for determining the camera pose.
The object of the invention is to provide a system and method of the type stated at the outset which permit in each case a largely exact representation of virtual objects with regard to reality.